Dial

• Approved Indications:
• Hypertension (essential hypertension)
• Angina pectoris, including chronic stable angina and vasospastic (Prinzmetal’s) angina
• Supraventricular tachyarrhythmias, including atrial fibrillation and atrial flutter (rate control)
• Hypertrophic cardiomyopathy (off-label in some regions)
• Off-label / Clinically Accepted Uses:
• Management of coronary artery spasm
• Rate control in atrial fibrillation or flutter in patients with preserved ventricular function
• Treatment of certain pediatric arrhythmias under specialist supervision

• Route: Oral and intravenous (IV)
• Adults (Oral):
• Immediate-release tablets: 30 mg four times daily, titrate as needed up to 90 mg four times daily
• Extended-release formulations: 180–240 mg once daily, titrate to max 540 mg/day
• Adults (IV):
• Initial bolus: 0.25 mg/kg over 2 minutes; may repeat after 15 minutes if needed
• Continuous infusion: 5–15 mg/hr, adjusted according to response
• Pediatrics:
• Dose individualized; often 1–2 mg/kg/day orally divided doses; IV dosing requires specialist management
• Elderly:
• Start at lower doses with careful titration due to increased sensitivity and clearance changes
• Renal Impairment:
• No dosage adjustment necessary, but monitor clinical response
• Hepatic Impairment:
• Use cautiously; dose reduction may be required due to decreased metabolism
• Administration Notes:
• Oral tablets should be taken with water; extended-release forms should not be crushed or chewed
• IV administration requires cardiac monitoring due to risk of hypotension or bradycardia

Diltiazem hydrochloride is a nondihydropyridine calcium channel blocker that inhibits the influx of calcium ions through L-type calcium channels in vascular smooth muscle and cardiac muscle. This action causes coronary and systemic arterial vasodilation, reducing myocardial oxygen demand by lowering afterload and heart rate. In cardiac tissue, it depresses sinoatrial (SA) and atrioventricular (AV) nodal conduction, resulting in decreased heart rate and slowed AV nodal conduction, beneficial for controlling supraventricular tachyarrhythmias.

• Absorption: Well absorbed orally; bioavailability approximately 40% due to first-pass metabolism
• Distribution: Widely distributed; volume of distribution approx. 5–7 L/kg
• Metabolism: Extensively metabolized in the liver via CYP3A4 to inactive metabolites
• Half-life: 3–4.5 hours (immediate release), extended-release forms allow once-daily dosing
• Elimination: Primarily biliary and renal excretion of metabolites; less than 5% unchanged in urine
• Onset of Action: Oral immediate-release: 30–60 minutes; IV: within minutes
• Steady State: Achieved within 2–3 days of regular dosing

• Pregnancy:
• FDA Category C — Animal studies show adverse effects on fetus; use only if potential benefit justifies risk
• Lactation:
• Excreted in breast milk in small amounts; caution advised
• Monitor breastfed infant for adverse effects such as hypotension or bradycardia

• Primary Class: Calcium channel blocker
• Subclass: Nondihydropyridine calcium channel blocker

• Known hypersensitivity to diltiazem or formulation components
• Severe hypotension (systolic BP <90 mmHg)
• Sick sinus syndrome or second- or third-degree AV block without a pacemaker
• Acute myocardial infarction with pulmonary congestion and left ventricular failure (relative contraindication)
• Concomitant use with intravenous beta-blockers (risk of severe hypotension or heart block)

• Use with caution in patients with impaired cardiac conduction; monitor ECG regularly
• Risk of worsening heart failure; avoid in patients with severe left ventricular dysfunction unless benefits outweigh risks
• Monitor blood pressure and heart rate to avoid hypotension and bradycardia
• Use cautiously in hepatic impairment due to reduced metabolism
• Avoid abrupt withdrawal to prevent rebound hypertension or angina exacerbation

• Common:
• Cardiovascular: headache, dizziness, flushing, peripheral edema, bradycardia, hypotension
• Gastrointestinal: nausea, constipation
• Serious/Rare:
• AV block or sick sinus syndrome
• Congestive heart failure exacerbation
• Hypotension leading to syncope
• Hepatotoxicity (rare)

• Major Interactions:
• CYP3A4 inhibitors (e.g., ketoconazole, erythromycin) increase diltiazem levels, risk of toxicity
• Beta-blockers (especially IV) may cause additive cardiac depression
• Digoxin levels may increase; monitor closely
• Carbamazepine and phenytoin may decrease diltiazem levels via induction
• Drug-Food: Grapefruit juice inhibits CYP3A4, increasing diltiazem plasma concentration
• Drug-Alcohol: May enhance hypotensive effects

• Guidelines support diltiazem for rate control in atrial fibrillation and management of hypertension and angina
• Recent recommendations emphasize monitoring for heart failure patients due to potential negative inotropic effects
• No significant changes in approved indications or dosing protocols in recent years

• Store at 20°C to 25°C (68°F to 77°F)
• Protect from moisture and light
• Keep tablets in tightly closed container
• Keep out of reach of children